Ikko (project page, download) is a little templating engine. Rich Kilmer wrote it, and Tom Copeland is maintaining it. It's very simple and is only suitable for small projects. Fortunately, there are many of those around :-)

Say you want to plug some HTML into a little page:

<html>
<body>
<!--Fragment key="name"-->
</body>
</html>

Put ikko.rb in the same directory as your script and write a little script: